It is known to equip plastic tanks, in particular, pressurized plastic fuel tanks (DKKB), with tie rods for absorbing tensile forces acting on the tank shells. The tie rods are usually manufactured from the same material as the tank shells, in particular from high density polyethylene (HDPE). Tie rods made of HDPE may be sealed into the tank shells during the production of the latter and are therefore inexpensive to produce.
A tie rod made of plastic is known, for example, from U.S. Pat. No. 6,338,420 B1, which discloses a plastic fuel tank for a motor vehicle, comprising a hollow plastic vessel body with a base and a top side and a plastic strut in the hollow vessel body, the top foot of which is fusion bonded to the top side of the tank and the bottom foot of which is fusion bonded to the base of the tank.
FIGS. 1a to 1c illustrate a known tie rod. The tie rod is produced in one piece from a plastic material such as high density polyethylene (HDPE). The end faces 1 and 2 of the tie rod therefore likewise composed of HDPE and may be welded to a plastic tank. The central part 3 of the tie rod is an HDPE solid material.
Tie rods made solely of plastic, however, exhibit swelling behaviour under the action of fuel, however, and therefore, the tie rods and herewith also the plastic tanks are deformed over time.